1. Technical Field
This invention relates to video cassette recorders (VCR's) which record color video signals. In a broadcast video signal, the horizontal synchronization pulse and luminance signal comprise the luminance portion of the video signal, while the chrominance signal and its 3.58 MHz subcarrier comprise the chrominance portion. A VCR includes a filter which separates the luminance and chrominance portions from one another for processing through separate channels.
2. Description of the Related Art
A well-known problem in VCR's is the limited playing time of a video tape cassette. Although the playing time may be increased by reducing the tape speed, the bandwidth and resolution of the resulting playback video signal decreases with the reduction in tape speed, due to the reduced tape-to-head velocity and the high-frequency limitations of video tape recording. A well-known technique for reducing incoming signal bandwidth, to permit recording at slower tape speeds, is to time division multiplex the luminance and chrominance signals of each horizontal line of the incoming video signal into separate time segments (one segment containing the luminance signal and the other segment containing the chrominance signal). Both segments are time compressed in order to fit them serially into one horizontal line scan period. Because the luminance signal contains the most important information (with respect to the resolution of the video image) its time-compression ratio is less, in order to accommodate a higher recorded luminance bandwidth. The less important chrominance signal has a greater compression ratio, typically by about a factor of four. Because the time-compression ratio of the luminance signal is less, its time-compressed recorded bandwidth is less, thus avoiding some luminance high frequency information being cut off by the bandwidth-limiting tape-to-head interaction.